Nikolay M. Loim

Metal-free and transition-metal tetraferrocenylporphyrins part 1: synthesis, characterization, electronic structure, and conformational flexibility of neutral compounds

H(2)TFcP [TFcP = 5,10,15,20-tetraferrocenyl porphyrin(2-)] was prepared by a direct tetramerization reaction between pyrrole and ferrocene carbaldehyde in the presence of a BF(3) catalyst, while the series of MTFcP (M = Zn, Ni, Co and Cu) were prepared by a metallation reaction between H(2)TFcP and respective metal acetates. All compounds were characterized by UV-vis and MCD spectroscopy, APCI MS and MS/MS methods, high-resolution ESI MS and XPS spectroscopy. Diamagnetic compounds were additionally characterized using (1)H and (13)C NMR methods, while the presence of low-spin iron(ii) centers in the neutral compounds was confirmed by Mössbauer spectroscopy and by analysis of the XPS Fe 2p peaks, revealing equivalent Fe sites. XPS additionally showed the influence on Fe 2p binding energies exerted by the distinct central metal ions. The conformational flexibility of ferrocene substituents in H(2)TFcP and MTFcP, was confirmed using variable-temperature NMR and computational methods. Density functional theory predicts that alpha,beta,alpha,beta atropisomers with ruffled porphyrin cores represent minima on the potential energy surfaces of both H(2)TFcP and MTFcP. The degree of non-planarity is central-metal dependent and follows the trend: ZnTFcP < H(2)TFcP approximately CuTFcP < CoTFcP < NiTFcP. In all cases, a set of occupied, predominantly ferrocene-based molecular orbitals were found between the highest occupied and the lowest unoccupied, predominantly porphyrin-based molecular orbitals. The vertical excitation energies of H(2)TFcP were calculated at the TDDFT level and confirm the presence of numerous predominantly metal-to-ligand charge-transfer bands coupled via configurational interaction with expected intra-ligand pi-pi* transitions.

First optically active organometallic free radical in the cymantrene series

Abstract Replacement of one CO ligand in the enantiomeric 2-methylcymantrenecarboxylic acid ester for a radical ligand PhS results in the preparation of stable and optically active odd-electron complex CH3C5H3COOCH3Mn(CO)2SPh]. fully characterized by electron spin resonance, mass spectroscopy, UV-visible spectroscopy, IR spectroscopy and circular dishroism spectroscopy. This is the first example of an optically active organometallic free radical.

P-Chiral monodentate diamidophosphites as ligands for Rh-catalyzed asymmetric reactions

A series of P-chiral monodentate diamidophosphite ligands of the 1,3-diaza-2-phosphabicyclo[3.3.0]octane family was tested in the Rh-catalyzed hydrogenation of dimethyl itaconate and addition of phenylboronic acid at the carbonyl group of trans-cinnamaldehyde. The enantioselectivities and conversions of these reactions are strongly dependent on the nature of the exo-cyclic substituent of the ligand.

BICYMANTRENYL CHEMISTRY 4. RESOLUTION TO ENANTIOMERS AND DETERMINATION OF THE ABSOLUTE CONFIGURATION OF BICYMANTRENYLCARBALDEHYDES

Planar chiral 2- and 3-bicymantrenylcarbaldehydes can be resolved to enantiomers through Schiffs bases with (S)-(−)-α-phenylethylamine. Optically active derivatives of bicymantrenyl with Me and CH2OH substituents were synthesized from (−)-3-bicymantrenylcarbaldehyde. The absolute configuration of Schiffs base obtained from (+)-3-bicymantrenylcarbaldehyde was determined by X-ray diffraction analysis.